Materials based on indium aluminum gallium nitride (InxAlyGa1-x-yN, x=0-1, y=0-1 and x+y=1), for example gallium nitride (GaN), are of great interest for use in semiconductor devices such as, but not limited to, high electron mobility transistors (HEMTs) due to excellent high frequency and power handling capabilities.
High thermal conductivity substrates, typically silicon carbide (SiC), are used in such devices in order to efficiently extract the heat and to minimize temperature rise of the device. In order to achieve high-quality heteroepitaxial growth of InxAlyGa1-x-yN on SiC, interfacial layers of the InxAlyGa1-x-yN type, x=0-1, y=0-1 and x+y=1, may be introduced between the InxAlyGa1-x-yN layer and the SiC substrate, and typically an aluminum nitride (AlN) nucleation layer is used to wet SiC substrate surface for two-dimensional nucleation process and to compensate for the lattice mismatch.
In order to use these materials in such applications, a high crystallinity of the InxAlyGa1-x-yN and AlN layers is of high importance.
Efforts to improve the crystal quality of an AlN nucleation layer sandwiched between a GaN buffer layer and a SiC substrate has been done and are discussed, e.g. by S. Qu and S. Li et al. in journal of Alloys and compounds 502 (2010) 417-422.
It is highly desirable to develop a semiconductor device structure with even further improved crystallinity of the constituting layers. Further, it is desirable to produce a semiconductor device structure with a reduced number of leakage current paths via structural defects like threading dislocations. Moreover, it is desirable to produce a semiconductor device structure with a reduced thermal boundary resistance (TBR).